1. Field of the Invention
The present invention relates to an apparatus and a method for providing a more dust-free environment, particularly for the production of semiconductor devices.
2. Description of the Related Art
FIG. 1 illustrates a known resin molding apparatus for resin-molding a semiconductor device. This apparatus is disclosed in Japanese Patent Laid-Open Publication No. 55-96642. This apparatus is provided in the center thereof with a press machine 1 which is equipped with an upper platen 2 and a lower platen 3 which are disposed to oppose each other. The upper platen 2 is fixed in place by means of tie-bars 4. The lower platen 3 is connected to a hydraulic cylinder 5 for sliding up and down the tie-bars 4 by the hydraulic cylinder 5. An upper mold part 6 of a mold is provided on the lower face of the upper platen 2, while a lower mold part 7 cooperating with the upper mold part 6 is disposed on the upper face of the lower platen 3, such that the upper and lower mold parts vertically oppose each other. The lower mold part 7 is provided with a plurality of cavities for receiving semiconductor chips bonded to a lead frame and a pot for receiving a tablet. These cavities are connected to the pot through runners. The upper mold part 6 also has a plurality of cavities corresponding to those in the lower mold part 7.
A loader 8 is disposed on a lateral side of the press machine 1 for supplying a lead frame and a tablet onto the lower mold part 7 of the press machine 1. An unloader 9 is disposed on the other lateral side of the press machine 1 for taking out the resin-molded semiconductor device from the press machine 1. A magazine 10 for storing finished semiconductor devices is disposed under the unloader 9. On the other hand, as shown in FIG. 2, a cleaner 11 is disposed behind the press machine 1 for the purpose of removing burrs of resin which become attached to the upper and lower mold parts 6 and 7 during the molding. A dust collector (not shown) is connected to the cleaner 11 through a duct 12.
The press machine 1, the loader 8, the unloader 9, the magazine 10 and the cleaner 11 are covered by a cover 13. As will be seen from FIG. 3, the cover 13 has a frame 13a provided on ridge portions of the resin molding apparatus and a thin plate 13b fixed to the frame 13a by means of screws 13c.
The operation of the described semiconductor resin molding apparatus is as follows. A lead frame (not shown) is prepared with semiconductor chips die-bonded thereto and with the electrodes of the semiconductor chips wire-bonded thereto. A tablet (not shown) also is provided. The lead frame and the tablet are fed onto the lower mold part 7 on the lower platen 3 of the press machine 1 by means of the loader 8. In this state, the semiconductor chips bonded to the lead frame and the tablet are respectively disposed in the cavities and the pot. Then, the hydraulic cylinder 5 operates to raise the lower platen 3 along the tie bars 4 so that the upper and lower mold parts 6 and 7 are brought together to close the mold. Then, the tablet received in the pot is heated and melted by a suitable heating means such as a heater. The molten tablet is forced out by a plunger or the like means and injected through the runners into the cavities, whereby the semiconductor chips are resin-molded.
The resin with which the semiconductor chip and the lead frame are sealed is then cooled and solidified. Subsequently, the lower platen 3 is lowered along the tie-bars 4 by the force of the hydraulic cylinder 5, so that the product is taken out by an unloader 9 and placed in the magazine 10. Subsequently, the resin burrs adhering to the upper and lower mold parts 6 and 7 are removed by the cleaner 11 and the resulting fine pieces of the resin are absorbed and collected by the dust collector through the duct 12.
This known apparatus for producing semiconductor devices suffers from the following disadvantages. Both the frame 13a and the thin plate 13b constituting the cover 13 covering the whole resin molding apparatus are rigid. Therefore, often a gap 13d is undesirably formed between the frame 13a and the thin plate 13b as shown in FIG. 3 due to the deflection of the thin plate 13b between adjacent fixing screws 13c and surface roughness between the frame 13a and the thin plate 13b.
Such a gap 13d undesirably allows, particularly when the pressure in the cover 13 is equal to or higher than the external pressure, various dust particles suspended by the air within the cover to be released to the exterior of the cover 13. The dust particles include fine pieces of resin produced after the removal of burrs, resin powder produced from the tablet and dusts generated by the actuator itself. In some cases, a blast of air is applied to the mold in advance of or simultaneously with the cleaning by the cleaner 11. As a result, the dust particles which have collected in the cover 13 are released to the outside of the cover 13.
For these reasons, the resin molding apparatus has to be operated in a clean room which is separated from the room in which the die bonding and wire bonding, steps of the same finishing process as the resin molding, are conducted. In consequence, difficulty is encountered in the design of a continuous process line which can automatically conduct all the steps of the process, including the resin molding, which are liable to be affected by dusts. The fine pieces of resin which could not be collected by the cleaner are scattered around the press machine, adversely affecting the durability of the actuator and sliding portions of the apparatus.